Author's note: The fandom trope of Mirajane running a betting pool has little basis in canon, but it's fun to explore the idea nonetheless.
Fairy Tail belongs to Hiro Mashima. I'm just borrowing his toys for a while.
Mirajane's role as the guild's bookie came into existence shortly after Lucy joined Fairy Tail.
She really started it for her own purposes. It was getting hard to keep track of individual bets with other members, especially when the other members were also making bets with each other, so putting together a proper betting pool seemed liked the most sensible solution. She had purchased a bookie's journal from the Magnolia horse races, and learned how to calculate the odds and payouts based on time of bets from the bookies there.
With their help, she had set up a formal framework for the betting pools.
The rules were simple:
* You cannot bet on yourself. (Juvia had tried anyway.)
* You cannot bet using insider knowledge. (This one was tricky; the odds of Gajeel and Levy had gone way up after Pantherlily dropped a large amount of cash on them, causing Mirajane to raise an eyebrow.)
* Older bets have a higher payout. (The first Natsu/Lucy bet, from none other than Erza, would earn the Titania more money than anyone else would see when it inevitably happened.)
* Long shot bets have a higher payout. (The first Natsu/Gray bet had started with three hundred to one odds, and it had only climbed higher over time.)
* One relationship per person at a time. If you want to change, you forfeit the original bet. (Lucy had lost a thousand jewels when she changed from Jet/Levy to Gajeel/Levy.)
* Bets are only payed out if the couple comes out officially. If the couple denies it, it's not considered formal.
The original betting pool, which had started with minor bets like "a thousand jewels on Gray/Cana before year's end" had turned into a monstrosity once Fairy Tail began absorbing other members from defeated guilds, and the teen aged members of the guild began to show interest in the opposite sex.
After Juvia joined, the majority of the Gray/Cana bets were canceled in favor of Gray/Juvia. Reedus, the one person who had stuck out for Gray and Cana, had seen his odds drop, but his potential payouts had increased exponentially as a result of less competition.
By far the biggest payout would be for Natsu and Lucy, with over one third of the total pot (which was at about two million jewels and counting) having to be doled out. Odds were currently three to one in favor. However, since pretty much everyone in the entire guild had placed that bet, their payout wouldn't be much more than their original pay in. Even Lisanna had five thousand jewels in on that one!
The betting pool's bank account had actually been tucked away safely during the lost seven years, as only Mirajane had access to it. Otherwise, the diminished Fairy Tail might have raided the cash store to help pay off their bills. She was rather grateful for that bit of foresight, even if it meant she owed almost hundred thousand jewels total to all the Bisca/Alzac folks once they returned. Odds had been ten to one in favor, so the payouts were small, but most people still made a profit once interest from the seven years was added in.
Some folks decided to really play the odds and include long shots. Mirajane smirked at the evenly divided bets over her choosing Laxus or Fried. Both men had showed slight interest, but neither had made a move yet, and she herself wasn't sure she wanted either of them to.
A very small number of guild members also had long odds on Natsu and Gray, Gray and Lucy, Lucy and Loke, Natsu and Lisanna, and some rather outrageous crack pairings that had virtually no chance in hell, but hey, it was their money to lose.
All in all, the infamous couples betting bracket was not only Mirajane's favorite hobby, it was an endless source of entertainment. She was not only the bookie, but also participated – inasmuch as she was allowed to, of course. The "insider knowledge" clause prevented her from betting on Elfman or Lisanna, but you can be sure she'd put a large sum on Natsu and Lucy the moment she'd opened up the books to the public.
It was only after Mirajane saw an unexpected sight - Mystogan comforting Erza after her enormous victory against a hundred foes - that Mirajane learned about a critical vulnerability in their little betting brackets.
She watched, astonished, as the masked man of Fairy Tail (or rather, his Earthland double) held the Titania's hand as she slept, recovering from her hard-won victory. The tender, adoring expression in his eyes above his mask made Mirajane do a double take.
When had that happened?
Curious, she flipped through her books to the Erza page. Erza/Natsu, Erza/Gray, Erza/Macao... There was a grand total of one entry for Erza and Mystogan/Jellal, dated prior to Tenrou Island, shortly after the Edo adventure when they'd learned about Mystogan's true identity.
Twenty thousand jewels on "Erza and Jellal disguised as Mystogan", with the note, "Call it a hunch."
Odds calculated at two hundred to one against at the time of entry.
Mirajane bit her lip. If that match up actually happened, the entire two million jewel pot would be cleaned out at once - they'd really owe her a lot more, but the pot's entire worth was the maximum that a person could get, regardless of the odds. No one had seriously expected a single person to win the entire thing. It would ruin the business, so to speak. The only other pairings that could break the bank like that were outrageous things like Natsu/Laxus.
Morbid curiosity had her flipping through the rest of the book, noting what other bets the sneaky little psychic cat had made. Natsu and Lucy, of course. Gray and Juvia. Elfman and Evergreen (here Mirajane winced.) Gajeel and Levy. Those last two pairings were also dated earlier than anyone else in the guild, long before the S Rank exams, ensuring that Carla would have the biggest payout. While it was plain as daylight to anyone that the script mage and the iron dragon slayer were just steps away from dating today, Carla had picked them out at a time when everyone else was pretty sure Levy still resented him being let into the guild at all. She'd put down two thousand jewels when the odds were still fifty to one against. Another million jewel payout. Ouch.
The betting pools were all rigged in Carla's favor, it seemed. She stood to make a lot of money when some inevitable pairings occurred. Maybe they should have thought of psychic magic when the "insider clause" was planned out, but the ability to see into the future, however uncontrolled, was not a magical gift that anyone but the little Exceed and her race's queen had, and Wendy and Carla had not yet joined the guild.
Mirajane hesitated when she came to her own page. Carla's predictions were usually somewhat right, if incomplete. No, she decided, fingering the paper. She would not look. She would prefer to leave her destiny up in the air, not have it decided by a little white cat with the ability to see the future.
With a sigh Mirajane closed the journal. There was always the possibility that Erza and Jellal would choose not to formally pursue a relationship, or would prefer to keep it quiet. Or perhaps Jellal would be outed as not really being Mystogan before anything further happened, voiding Carla's very specific bet. Fairy Tail would be in deep trouble with the Council if they were found out to be harboring Jellal, so they'd have worse things to worry about than their betting pool being drained - but Mirajane knew Jellal would do everything in his power to prevent that from happening.
Judging by the gentle look in Jellal's eyes as he watched Erza rest in the infirmary bed, the odds of something developing between the two were getting higher by the day. It would really depend on Erza, at this rate. Had she forgiven him?
That question seemed answered when Erza, stirring in her sleep, reached up to give her watcher a sweet peck on the lips before falling back onto the bed with a satisfied smirk. The queen of the fairies had earned her rest.
Mirajane dutifully looked away as Mystogan glanced furtively around the room, checking to see if anyone had seen that. Oh yes, they were smitten with each other.
And Carla had foreseen that it would happen long, long ago.
The demon mage smiled.
Well played, little Exceed. Well played.